An Overview: Synthesis of Menthol using Heterogeneous Catalysis

Essential oils are widely used in cosmetic and personal care products. These essential oils such as menthol, limonene, rose oil, and jasmine oil are extracted from plants and also prepared in the laboratory. Menthol is the most common cyclic monoterpene alcohol, which has been produced due to its demand in various industries worldwide. In the literature, there were many protocols reported for the synthesis of menthols from natural or synthetic precursors. In this review, we summarized the synthesis of menthol from citral, citronellal, and pulegone using various heterogeneous catalysts under different conditions. Considering the world's demand for menthol in food preservatives and scents, the right optimization of citronella extraction and its conversion is highly important. It can be used in pharmaceutical industries due to the presence of active substances. The presence of flavored compounds has the potential to enhance the nutritional value of food. This review will be very helpful for researchers who are working on menthol synthesis in industry and institutions. The determination of direct conversion to menthol over indirect conversion can be proven to be effective for industrial use as it will be more economical and time-saving.